Telephone system.



F. B. ALLEN.

TELEPHONE SYSTEM APPLICATION FILED D130. 6, 1909.

Patented Aug. 8;;1911;

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FRANK B. ALLEN, 0F ELYRIA, OHIO, ASSIGNOR TO THE DEAN ELECTRIC COMPANY,OF ELYRIA, OHIO, A CORPORATION OF OHIO.

TELEPHONE SYSTEM.

Specification of Letters Patent.

Patented Aug. 8, 14911.

r Application filed December 6, 1909. Serial No. 531,646.

To all whom it may concern:

Be it known that I, FRANK B. ALLEN, a citizen of the United States,residing at Elyria, in the county of Lorain and State of Ohio, haveinvented certain new and use ful Improvements in Telephone Systems; andI do hereby declare the following to be a full, clear, and exactdescription of the invention, such as will enable others skilled in theart to'which it appertains to make and use the same.

My invention relates to telephone systems and more particularly to whatare known as divided central or trunking systems. In such systems twocentral oflices remote from each other are connected by a trunk circuitwhich, through an interposed central station circuit, is used to connecttelephone lines terminating at the different central stations. Thevarious operations which complete this connection are made by twooperators, and are controlled by a system of signals which depend uponthis operation and which, if followed, insure the success of theconnections without inconvenient complications or unnecessary actions onthe part of the operators. My invention relates to such a system, and Iendeavor to simplify the same by improving the system of signaling nowin use. More particularly, I introduce apparatus and circuits soarranged and connected as to give a distinctive signal to both thecalling subscriber and the central station at which his line terminates,whenever the called line to which the trunk circuit is connected, isalready in use.

In systems of this character the central station at which the callingand call-initiating line terminates, is known as the A exchange and theend of the trunk circuit there, the outgoing end. The other end of thetrunk is known as the incoming end, and the central stat-ion therein,the B exchange.

Other objects and purposes of my invention will be clear from theparticular description. I have explained these as being the principalobjects I intend to accomplish, but I do not desire to be limitedthereby.

My invention will be best understood by reference to the followingdescription when taken in connection with the accompanying illustrationshowing one specific embodiment thereof, while its scope will be moreparticularly pointed out in the appended claims.

The figure is a diagram of the circuits and apparatus composing myinvention in normal condition.

In the upper left hand corner I show a subscribers line terminating inmultiple jacks at the A exchange. At A I show a cord circuit terminatingin plugs and adapted to connect the subscribers line with a second line;or, as shown in the figure, a trunk circuit terminating upon the sameboard in a jack J At R and R I show the line and cut-ofi relays of thesubscribers line; and at L, the line lamp. R R R and R are thesupervisory relays controlling the supervisory lamps L and L At P and PI show the answering and calling plugs respectively. The functions ofthese parts will be clear from the description of the operation to begiven later on.

The trunk line W extends from the A ex change where its outgoing endterminates in the jack J to a second or B exchange where its incomingend terminates in the plug P The trunk circuit is conductively separatedand inductively connected at the induction coils I and I the windings ofwhich are in each side of the trunk. The winding of the coil I and thatof I in each side of the trunk are separated by the condensers K and Kinterposed in the outgoing and incoming ends respectively.

. At R I show a trunk relay connected in the outgoing end side of thetrunk in bridge of the condenser K and normally in circuit with theresistance X. At R I show a subscribers relay which is adapted to becontrolled by the called subscriber or by an automatic circuit breaker.

L is a combined guard and ringing lamp, which, in its guard capacityserves to indicate that the plug P has been inserted into the ack J and,in its ringing capacity, serves to indicate to the B operator theresponse of the called subscriber to the calling signal. I

L is a disconnect lamp serving to apprise the B operator of thewithdrawal of the plug P from jack J R is a relay controlling circuitsat the incoming end and which, for the sake of convenience, I call theterminal relay. R is a second relay controlling circuits of the samecharacter which T call, for the sake of convenience, a second terminalrelay.

B is a relay which, for the sake of convenience, I call the controllingrelay and which is utilized for the purpose of making and interruptingthe circuits during the connections.

R is a relay controlling the connections of the automatic busy testapparatus, and which I call, for the sake oi convenience, the testrelay.

R is a relay which controls the connection of the signaling current andwhich I call the signaling relay.

Y is a continuously rotating commutator which automatically makes andbreaks the circuit of the signaling relay whereby the signaling sourceis alternately connected and disconnected from the line during suchperiods of time.

At M, M M and M I show sources of current which are adapted to producecurrents of different distinctive characteristics to which the signalreceiving device at stations on a party line are adapted to respond. N,N, N and N" are the ringing switches which are controlled by keys toconnect these machines to the line.

1*." and N are the master keys which are depressed each time any of theringing springs N, N N or N is operated.

At Z I show a continuously operating circuit break-er consisting of apendulum e which oscillates continuously making and breaking a circuitincluding the secondary of the induction coil T The primary of thisinduction coil is connected in circuit with rheotome V. The pulsatingcurrent produced by this rheotome is interrupted at intervals by theinterrupter Z, so that the current is imposed upon the line for certainintervals only.

On the right hand side of the figure I show a telephone line upon whichthere are tour substations, which terminated at the 13 exchange in themultiple jacks J Each of the stations is provided with a signal deviceresponsive to the particular character of current produced by one of themachines M, M M or M B and R are the cut oil and line relaysrespectively in this line, and L the line lamp thereof. Stations uponthis line are indicated at D, D, D and D The apparatus, the circuits andthe funct-ions of the same will be best understood by a description ofthe operation of the system.

The operation is as follows: Supposing the subscriber at the station 0in the upper left hand corner desires to talk with the subscriber at thestation D upon the line at the right of the figure. The subscriber at Cremoves the receiver E from the hook H, conipleting the followingcircuit: from positive side of B *123-H- transmitter l5 back to B Thisenergizes the relay It which pulls up the armature 7 closing the switch78 and completing a circ'uit through the lamp L as follows: positiveside of B 9LS7-back to B". This lights the lamp L. The A operatorinserts the plug P into the jack J, completing a circuit, from G B--l0-R 1l-12-R 1- to ground at G. This energizes the relay breaking thecircuit of the lamp L at 15-- 1G. The circuit through the relay lt is asfollows: G winding of R 17 l8l9- 21 2 3 H T 4t22-23-24 25 winding of RQG battery B to ground. The A operator then throws her listening keywhich connects her head set (not shown) in circuit with the subscriber Cat the switch 27'28. Having ascertained from this subscriber that thesubscriber D is wanted, she calls up and communicates with the B erechange operator over a separate order wire (not shown), and having beeninformed that the trunk W is the one to be used, she im mediatelyinserts the calling plug it of her cord into the jack J of the trunkit". In connections of this character the insertion oat the plug at theoutgoing end generally takes place before that at the incoming end, asthe A operator is ready with the plug or her cord circuit wheninstructed to use a ticular trunk. The insertion of the plug P- into theack J completes a circuit through R as follows: G battery B 29 R303l-3233 to ground G it" pulls up its armature 3d closing switch andcompleting a circuit through the lamp L as follows GL 3 G373 5-3l-29-- Bto ground G Over this the lamp L is lighted. A second circuit iscompleted as follows: ground at G winding of relay Tt tO-llt2l:3-X-t4:-R4:5-tltit"-4-8-4t9505l52 winding of R" 53battery B toground G Owing to the presence of the 'esistance X in this circuit, thecurrent flow therein is not su'liicient to operate the relay B, so thatthe lamp L continues to burn after the comple tion of this circuit. Therelay it is operated pulling up its armature 60, closing the switch60-61 and lighting the lamp L over the following circuit; ground G*I3*--G0- (31-62636 tL* to ground G. The operation of L informs the Boperator that the connection at the outgoing end has been made. Shefirst tests the called line by applying the tip 62 of the plug P to thering par- 63 of the called line. If this line is busy, the ring will beat a potential above that of ground, and impulses of current will passthrough 62'6 i-'65'66676869 707 1 to the contact 72 to which the testdevice is connected. Assuming that the line is idle, the B operatorinserts the plug P into jack J and depresses the ringing key at N whichis adapted to connect up the machine M which we will assume produces acurrent of the character to which the bell S at the station I),responds. At the operation of the spring N, the master spring N and Nare operated. A circuit is then completed from ground G 73R -6379 75R-77N-B G This energizes the cut-off relay R which attracts its armatures80 and 81, cutting off the called line from the line relay and signal.Relay R is energized, pulling up the armature 71 closing the switch 717&and cutting off the test apparatus at 7172. The armature 75 isattracted, closing the switch 757 6 and locking the relay R upon battery13, making the subsequent operation of the relay dependentupon the plugP This relay also draws up the armature 77, closing the switch 7778 inthe circuit of the lamp L. By this operation the relay R is energizedfrom G- 73 R 63- 79 75 808182-83- R N8%858687B to ground G. This pullsup the armature 88 opening the switch 8889; armature 90 looking therelay R on the battery B by closing the switch 90-91 and pulling up thearmature 92, closing the switch 92-93 in the circuit of the signalingrelay R. If the contacting segment of the commutator Y is on, and, ifnot, as soon as it comes on, a circuit is completed through the ringingrelay R as follows: G Y9et-93-9295R 62 616OB to ground G This circuit,as described, is alternately made and broken by the commutator. Therelay R pulls up its armatures 6 1 and 96, interrupting the trunkcircuit at and 97, and closing the signaling circuit as follows: fromground G through MN-989996100101 ground G". This operates the signal Sand the subscriber at D responds by removing the receiver E from thehook H As soon thereafter as the relay R is deenergized by the advent ofthe insulation upon the commutator Y, a circuit is completed through therelay R as follows: G B* winding of R -110-111'11211397- 96 100 101 102E 11%H T 103 10d 62 6t' 65 66 67 68. 6970 winding of R 7174 to ground G.The relay R is energized, pulling up the armature 115, closing a shunt116 about the resistance X, removing this resistance from the circuit ofthe relay R which is energized, pulling up its armature 37 andextinguishing the lamp L which indicates to the A operator that thecalled subscriber has responded. The relay R also pulls up the armature117, closing the switch 117 118 and completing a circuit through therelay R as follows: ground at G B 75 -76R 118-11780-7579- 63- 73 toground G The relay R pulls up the armature 120, breaking the switch 120-121. The armature 63 is attracted, breaking the circuit of the lamp Land extinguishing the same. The armature 82 is attracted, locking relayR through 81 and 80. R also draws up 82 breaking the circuit of R anddisconnecting the ringing current from the line. The subscribers are nowcon nected for conversation which takes place as follows: throughtransmitter T at station Cl:-222821 condenser K 515O 491745 through theinduction coils t3J and P K 1819 212-E- 3H back to T. These currents areinduced into the other side of the trunk through the coils I and 1 Thisside of the talking circuit is traced as follows: T10310462665'-66676869 through the windings of the coils I and I 110 111112 1l39796100101 1O2E 11 1H back to T When the conversation iscompleted the subscribers hang up their receivers, the circuit of therelay R is broken, the lamp L lighted and the A operator pulls down plugP restoring the left hand portion of her cord to normal, The relay R isde'energized permitting the armature 115 to fall back breaking the shuntof the resistance X which causes the lamp L to be lighted, whereupon theA operator pulls out the plug P restoring the cord circuit to normal.The relay R is thus de'energized, allowing the armature 60 to fall backupon the contact 130, completing the following circuit: G B 60130-131-7778L*G lighting the lamp L which gives the disconnect signal andthe B operator who immediately pulls out the plug P interrupting thecircuit of the re lays R and R which restores the system to normalcondition.

In the operation of systems of this character the B operator will oftenfail to test the line before inserting the plug of the trunk into thejack of the called line; or, as is possible with my system, it may beintended that she shall connect without testing. Assuming that the lineat the right hand side of the figure is busy, that is, that a plug ofsome cord circuit is inserted in one of the multiple jacks of the lineand the B operator inserts the plug P into the jack J The ring 63 willbe at a potential higher than ground, owing to the presence of the plugof the cord circuit in the niulre G to ground G The relay R will beenergized pulling up its armatures 87, (38 and 111. The switch 86-87 isopened, preventing the making of a circuit through B when the masterspring N is actuated. The armature 87 engages the front contact 1.36,completing a locking circuit through the relay it as follows: ground G-B S'Y-liltl-Qlt 79 63 R T3 to ground G The trunk circuit is broken at(5l'- 62?l, 1llll2, and the Vibrator Z connected in the trunk circuit atl1l-137 and oil-1138. 'lhe vibrator constantly opens and closes theswitch l .-,0-1 l1, and a second switch 142141. This second switchclosed before the first and opened thereafte A condenser K in a shunt143 of the switch 1-tG-1-l1 is controlled by the latter contacts. Theobject of this is to take up the discharge of the circuit and preventsparking at the contacts. The rheotome V is working constantly, puttinga tone upon the secondary of the induction coil 1 This tone isconstantly being interrupted by the vilu'ator Z so that short series ofimpulses only are placed. upon the trunk circuit through the followingconnection: beginning at the contact 14lOl l ll38-68 69 the primary ofthe coil ll* primar-y of the coil P-l10-llll371l5- secondary ofinduction coil I 141. These impulses are induced into a circuitincluding the receiver E which consists of the folhiwing connections:beginning at K the secondary of the induction coil l at5-l6-'Z'--t9-5()51-l -2l -29r-lT lit? -22l-l 91 SK -4l 12 l 3 seconda )y ofthe induction coil 1. This apprises the subscriber at the station C ofthe fact that the calledator line is busy, whereupon he would return hisreceiver to the hook giving the disconnect signal to t-heA exchange. TheB operator being unaware of the automatic busy signal, will depress theproper ringing key which operates the switch i \"-77, completing acircuit through the relay R plug P and jack J as already traced. Therelay will lock itself on the battery and will close the switch 'i l-7l.lllach time the switch 1l01 l1 is closed. the relay R will be energizedover the following circuit: grounc G battery 5 winding of Rl10-l11137li5 l4l-l-l-iE-O "l-13868 69-70winding of lt -717l ground GEach time the circuit is made the shunt 116 of the resistance X will beclosed and the relay operator, with the result that the lamp L will heflashed before the A operator which is a si 'nal to her that thecalled-for line is busy. She then pulls out the plug P which will causethe actuation of the disconnect signal and the taking down of theconnections at the B exchange. When the relay It is first actuated, acircuit will be completed from the battery B relay R switch 1l8-l17- dto ground previously described. This relay, when once actuated locksitself on the battery B retiring the ringing signal L While l have showncircuits and apparatus of this particular arrangement, which is the onesuggesting itself to me as being the most convenient, I do not desire tobe bound thereto as it will be obvious to those skilled in the art thatnumerous and extensive departures from the form and details of theapparatus here shown, may be made without departing from the spirit ofmy invention, the same being herein shown solely for the purpose ofclearly illustrating one specific embodiment thereof.

I claim- 1. In a telephone system, a plurality of telephone lines,circuit connections for connecting said lines together forconversational purposes, automatic means in said circuit connections forgiving a busy back signal. to the calling subscriber, electric switchesfor connecting said means to said circuit connections, said circuitconnections being normally continuous through said switches and meansfor operating said switches to inter rupt said circuit connections andconnect said automatic means in. circuit back of said interruption whensaid circuit connections are connected. to a busy line.

2. In a telephone system, a plurality of tClGUllOIlB lines, a centralstation, a sub central station, each of said lines terminating at one ofsaid stations, a central station connection circuit, a trunk leadingfrom one central station to the other, said central station connectioncircuit and said trunk adapted to cooperate to connect a calling and acalled line, an. automatic busy signaling means associated with saidtrunk, switches for connecting said means in cir cuit with said trunk,said trunk circuit nor mally continuous through said switches and meansoperating when said trunk is connected with a busy line, to interruptsaid trunk circuit and connect said automatic means to signal thecalling subscriber.

In a telephone system, the combination of a pair of central stations, aplurality of telephone lines each terminating at one of said centralstations, a trunk line having an outgoing end at one central station, anincoming end at the other and extending between said stations, a signalat said incoming end serving as both guard and ringing signal, a ringingkey and means for auto matically retiring said signal when the trunk isconnected with a busy line and said key is operated.

4. in a telephone s stem, the combination of a pair of central stations,a plurality of telephone lines each terminating at one of said centralstations, a trunk line having an outgoing end at one central station, anincoming end at the other and extending between said stations, a signalat said incoming end serving as both guard and ringing signal, a ringingkey and an automatically actuated relay for automatically retiring saidsignal when the trunk is connected with a busy line and said key isoperated.

5. In a telephone system, the combination of a pair of central stations,a plurality of telephone lines each terminating at one of said centralstations, a trunk line having its outgoing end at one of said stations,its incoming end at the other and extending between said stations, alamp serving both as a guard and a ringing signal in the incoming end, arelay at said end controlling the op eration of said signal and anautomatically operating circuit maker controlling said relay, saidcontrolling apparatus adapted to retire said signal when said trunk isconnected with a busy line.

6. In a telephone system, a plurality of telephone lines, a centralstation, a link conductor thereat, a sub-central station, each of saidlines terminating at one of said central stations, a trunk circuitconnecting said central stations, a supervisory relay at said centralstation associated with said link conductor adapted to be connected incircuit with said trunk, a resistance in said trunk governing theoperation of said relay, means in said trunk circuit adapted to changethe association of said resistance with said trunk when the trunk isconnected with a busy line, whereby said supervisory signal is gov ernedto indicate said busy condition at the central station.

7. In a telephone system, a plurality of telephone lines, a centralstation, a subcentral station, each of said lines terminating at one ofsaid central stat-ions, a trunk circuit connecting said centralstations, a supervisory signal at said central station, a resistancedevice associated with said trunk governing the operation of saidsupervisory signal, a relay associated with said trunk controlling theassociation of said resistance device with said trunk, a circuit forsaid relay, an automatic device for making and breaking the circuitthrough said relay when said trunk is connected to a busy line, saidrelay changing the association of said resistance device with each operation whereby said supervisory signal is operated to give the busysignal to the central station.

8. In a telephone system, a plurality of telephone lines terminating atcentral stations, a trunk circuit connecting said stations terminatingin a plug, jacks for said telephone lines, an automatic lousy signalingmeans associated with said trunk but normally disconnected therefrom, arelay adapted to connect said means in circuit with said trunk to signala calling subscriber when the plug of the trunk is inserted into thejack of a busy line and a supervisory signal at said central stationcontrolled by said automatic means to indicate said busy condition tothe main operator.

9. In a telephone system, a plurality of telephone lines terminating atcentral stations, a trunk circuit extending between said centralstations adapted to connect said telephone lines for conversation, asignaling switch associated with said trunk circuit, a switch forconnecting said trunk to a called line, an automatic signaling meansadapted to signal the calling subscriber when said trunk is connectedwith a busy line, a supervisory signal associated with one of saidcentral stations adapted to indicate the busy condition of the calledline to the operator at that central station, said supervisory relaycontrolled to give said signal by the automatic means and the signalingswitch jointly.

10. In a telephone system, a main central.

station, a sub-central station, a plurality of lines each terminating atone of said stations, a trunk circuit connecting said central stations,a supervisory signal associated with said main central station andadapted to be controlled over said trunk, a relay in said trunkcontrolling the operation of said signal, a circuit for said relay, asignaling switch controlling the circuit of said relay, an automaticcurrent interrupter normally disconnected from said relay circuit, and asecond relay adapted to connect said interrupter in circuit with saidsignal controlling relay when the trunk circuit is connected with a busyline.

11. In a telephone system, the combination of two central stations, aplurality of subscribers lines each terminating at one of said stations,a trunk line having an outgoing end at one of said central stations, anincoming end at the other and extending therebetween, a signal at theincoming end serving as both a guard and a ringing signal and meansacting automatically when the trunk is connected to a busy line toprevent said signal performing the latter function.

12. In a telephone system, the combination of a main central station,telephone lines terminating thereat, a sub-central station, telephonelines terminating thereat, a

trunk circuit having an outgoing end at said main central station, anincoming end at the sub-central station and extending therebetween, asignal at the incoming end serving both as a guard and a ringing signal,said signal operated when said trunk is connected in a circuit at themain station and means to prevent said signal serving the function ofindicating the ringing connection when the trunk is connected to a lousyline.

13. In a telephone system, the combination of a pair of centralstations, a plurality of telephone lines each terminating at one of saidcentral stations, a trunk circuit extending between said centralstations, switches at the central station for connecting said trunk inconversational. relation with said telephone lines, an automatic devicefor signaling a calling line when said trunk is connected inconversational relation with a busy called line, and locking means formaintaining said connection until such relation is disturbed.

1a. In a telephone system, the combination of a central station, asubcentral station, telephone lines terminating at each, circuitconnections extending between said central stations adapted to connecta. line terminating at each said central stations in conversationalrelation, an automatic signaling device associated with saidcircuitconnections, means in said circuit connections for connectingsaid automatic device in said circuit connections when a calling line isconnected in conversational relation with a busy line and. locking meansfor maintaining such connection.

15. In a telephone system, the combination of a central station, asub-central station, subscribers lines terminating at each of saidstations, a trunk line extending between said central station adapted toconnect telephone lines in conversational relation, a switch at one endof said trunk for connecting said trunk to a called line, means forautomatically signaling the calling line when said switch is operated toconnect it in conversational relation with a busy line, and means formaintaining said automatic signaling until said switch is restored.

16. In a telephone system, the combination of a central station, asub-central station, telephone lines teri'ninating thereat, a. trunkcircuit extending between said stations and adapted to connect telephonelines there at in conversational relation, a switch at saidsiiib-central station adapted to connect said trunk with a called line,an automatic busy signal device associated with said trunk circuit, arelay adapted to connect said automatic device in said trunk when saidswitch is fully operated, and a locking circuit for said relay.

17. In a telephone system, the combination of a central station, asub-central station, telephone lines terminating thercat, a trunkcircuit extending therebctween, a switch at one end of said trun adaptedto connect it. with a called line, means associated with said trunk forsignaling the called subscriber when the trunk is connected with a busyline, a relay for connecting said signaling means in said trunk when theswitch is operated to connect the trunk with a busy line, and a lockingcircuit for said relay controlled by said switch.

In testimony whereof I atliX my signature in presence of two witnesses.

FRANK B. ALLEN. Witnesses F. O. RIGHEY, C. A. SEVEROOOL.

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